I am having the same problem. I am using root as the user, all information checks is the pre=install window, and I still get that message. I am installing on a LAMP (fedora 13). I have even disabled selinux and still it does not install.

What are you inputting for the connection? If it's what I think you're referring to then you only need to input localhost. You may also use 127.0.0.1 which is basically the same thing. That normally does the job. Without having more details that's the best I can offer at this point.

FYI on some systems (BSD for example) MySQL isn't default configured to have a tcp listening socket.
But that should not be the case in any LAMP stack found in FC.
If your using a Windows/OSX LAMP stack to test possibly you need user root password blank ? I know a few of them are like that by default

I had the same problem and I finally tried connecting to the database as root and it worked. This is not recommended however. When creating the mysql user I used a wildcard (%) as host. Using phpmyadmin specify the host for your user as 'localhost' and '::1'. You will notice that the root user has the same designations. This will allow you to connect to the database as the user you created for the concrete5 database.

I had the same problem and I finally tried connecting to the database as root and it worked. This is not recommended however. When creating the mysql user I used a wildcard (%) as host. Using phpmyadmin specify the host for your user as 'localhost' and '::1'. You will notice that the root user has the same designations. This will allow you to connect to the database as the user you created for the concrete5 database.